Purification of alcohols by treatment with anhydrous lewis acids



March 12, 1968 -rs ET AL 3,373,211

PURIFICATION OF ALCOHOLS BY TREATMENT WITH ANHYDROUS LEWIS ACIDSOriginal Filed Dec. 28, 1962 DRYING COLUMN LEWISACID TREATMENT ZONE WASHTOWER 4 ALCOHOL PLUS DIMER AND TRIMER PRODUCTS HYDROCARBONS AND LIGHTBOILERS CRUDE ALCOHOL FEED-*1 Ml VENTORS RHEA N. WA 77305054550 5 YBEULAH SMITH M775 DAV/D EDWARD GENSHE/MEH JOSEPH KERNMERTZWE/LLER UnitedStates Patent Ofiice 3,373,211 Patented Mar. 12, 1968 3,373,211PURIFICATION OF ALCOHOLS BY TREATMENT WITH ANHYDROUS LEWIS ACIDS Rhea N.Watts, deceased, late of St. Francisville, 1.21., by Beulah Smith Watts,legal representative and sole heir, St. Francisville, La., David EdwardGensheimer, Calvert City, Ky., and Joseph Kern Mertzweiller, BatonRouge, La., assignors to Esso Research and Engineering Company, acorporation of Delaware Continuation of application Ser. No. 268,167,Dec. 28, 1962. This application Oct. 31, 1966, Ser. No. 591,019

8 Claims. (Cl. 260-643) This application is a continuation of Ser. No.268,167 filed Dec. 28, 1962 and now abandoned which is in turn acontinuation-in-part of Ser. No. 807,860 filed Apr. 21, 1959, and nowabandoned.

This invention relates to a process for treating alcohols which arecontaminated with carbonyl compounds. In particular this inventionrelates to a method of treating the aforenoted alcohols to clean upcontamination and to provide a purified productsuitable for theproduction of substantially colorless plasticizer ester.

The ever expanding use of plasticizer materials such as vinyl chloridepolymers or copolymers, polyvinyl acetate, cellulose esters, acrylateand methacrylate resins, rubbers such as the emulsion copolymers ofbutadiene and styrene or acrylonitrile or the copolymers of isobutylenewith small amounts of a diolefin such as isoprene, has created a largedemand for suitable plasticizers. Branched chain alkyl organic estersand particularly alkyl phthalic acid esters and more particularly octyland decyl phthalates, as well as the corresponding esters of maleicacid, adipic acid, azelaic acid, glycollic acid, sebacic acid or theiranhydn'des, have been known to be eflicient plasticizers for theaformentioned high molecular weight materials. The phthalic esters,however, are characteristic of this aforesaid group and color problemsresulting from the employment of contaminated alcohols will be observedregardless of the particular dibasic acid utilized in the esterificationreaction. In general, therefore, the esterification reaction forproducing plasticizeresters with alcohols is between an organic dibasicacid and/or its anhydride with the desired alcohol.

The above plasticizer esters are generally prepared by theesterification of a suitable alcohol, e.g. C C with an acidic reactantsuch as phthalic acid, the anhydride thereof or any of the acidicreactants noted above. The alcohol is employed in amounts fromstoichiometric to substantial excesses and heated, in accordance withone known process in the presence of an acid catalyst such as sulfuricacid, benzene sulfonic acid, toluene sulfonic acid, naphthalene sulfonicacid or the like. Alternatively, the acid and alcohol may be reacted athigher temperatures in the absence of any catalyst or sometimes withvery small amounts of catalyst. Entrainers or azcotrope formers may beutilized in the reaction to effect the removal of Water at lowertemperatures. Entrainers usually employed are the low boiling aromaticssuch as benzene, toluene, Xylene and the like, paraffinic hydrocarbonsof suitable boiling points, eg heptene and octane or olefinic materialssuch as diisobutylene, etc. Other acid and alcohol reactants are knownand are amply set forth in the abundant prior art.

One of the primary difficulties encountered in the manufacture ofplasticizer esters, especially where C and C alcohols are employed, isthe failure to obtain colorless products even when relatively highpurity reactants are employed. It has been known for some time thatsulfur contaminants result in oif-color ester products and more recentlyit was discovered that carbonyl compounds such as aldehydes. even invery small amounts, effect to a marked degree the color of the finalester product. To

counteract the degradation of color resulting from these contaminants,many commercial esterification processes employ mild conditions andcarefully control the reaction medium. Thus mild p-toluene sulfonic acidis often employed in lieu of sulfuric acid and the reaction mixture iskept free of oxygen usually by blanketing the system with CO or otherinert gases. Even with mild conditions a poor quality alcohol willresult in an oil-color ester product.

ermal esterification, on the other hand, results in color degradation ofthe product due to the contaminants in the reactants. Since no catalystis used, higher temperatures necessarily are employed which result inoff-test product depending on the amount of contaminant present.

A principal source of alcohols for the manufacture of plasticizer estersis via the one or carbonylation route where an olefin is reacted withcarbon monoxide and hydrogen in the presence of a catalyst, generally acobalt salt, at elevated temperatures and pressures to form an aldehydeproduct having one more carbon atom than the starting olefin. Thisaldehyde product is then freed of cobait and subsequently hydrogenatedto form the corresponding alcohol product. While the sulfur contaminantsintroduced into the product by either the olefin or the hydrogenationcatalyst, etc., may be effectively cleaned up by caustic washing,extensive distillation and similar treatments, the final alcohol productobtained in general will contain suificient amounts of contaminants toseriously affect the utlimate color characteristic of any ester preparedtherefrom. The term carbonyl compound is employed herein to mean thosesaturated or unsaturated compounds containing a O H C radical and thosecompounds which readily form aldehydic compounds. OX0 alcohols evenafter extensive fractionation will contain generally from 0.01 to 1.0wt. percent of carbonyl compounds. Dimer alcohols prepared by a modified0X0 route are also valuable as intermediates in the preparation ofesters and are subject to the same contamination problems as theordinary oXo alcohols. OX0 octyl alcohol, or as it is commonly calledisooctyl alcohol, comprises major amounts of dimethyl-l-hexanol andminor amounts of methyl l heptanol and smaller amounts of miscellaneousbranched alcohols. Oxo decyl alcohol also varies in isomericcompositions; however, it comprises predominantly primary trimethylheptanols.

Other OX0 alcohols employable in the esterification reaction of thisinvention include isohexyl, tridecyl and the like. Although a singleisomer may be separated from the 0x0 product, this is rarely done. Theone alcohols are almost always employed in their natural combination ofisomers as derived from the carbonylation synthesis. A list of typicalisomeric alcohols obtained during the 0x0 process may be found on page 7of the book entitled Higher OX0 Alcohols by Hatch, published by EnjayCo., 1957.

Another potential commercial source of alcohols suit.- able for thepreparation of plasticizers is viav the alkyl metal route. Thisrelatively. new process comprises basically the addition of ethylene orother olefin onto a metal alkyl such as aluminum triethyl or aluminumtriisobutyl to prepare high molecular weight aluminum trialkyl compoundswhich in turn maybe oxidized to form the corresponding aluminumalcoholates and finally hydrolyzed to form the alcohol. The alcoholsobtained via this new route also contain substantial quantities ofcarbonyl compounds which are either not separable from the alcohol orseparable only with extensive costly treatment. Alternatively the alkylmetal may be made directly by reaction of olefins with metal and H Analkyl metal of this type is easily converted to alcohols in the mannerdeand for the purpose of defining with more particularity some of thealcohol sources, reference may be had to US. Patent No. 2,637,746 toParker, which describes in detail the oxo process, and to a copendingcommonly assigned application, Ser. No. 808,933, filed Apr. 27, 1959,now Patent No. 3,030,402, which is a continuation-in-part of Ser. No.578,902, now abandoned, which describes one process for preparingalcohols via the alkyl metal route.

It has now been found that carbonyl contaminated alcohols and especiallyoxo alcohols containing in general from 6 to 16 carbon atoms may bepurified or upgraded by treatment with substantially anhydrous Lewisacids. The term Lewis acid is well known in the art as may be seen frompages 140, 177, 573 and 577 of Organic Chemistry by Fieser and Fieser,2nd ed. (1950), D. C. Heath and Company. The term anhydrous Lewis acidsas used herein includes in general transition metal halides such asaluminum chloride, aluminum bromide, tin chloride, tin halide, ferricchloride and zinc chloride in substantially Water-free or anhydrousform. Other Lewis acids equally applicable to the present processinclude anhydrous boron trifluoride, hydrogen fluoride (anhydrousliquid, B.P. 194), sulfuric acid (96%), anhydrous phosphoric acid andphosphorous pentoxide. The exact mechanism of this decontaminationprocedure and theory is not known; however, it is believed that thecontaminants in the alcohol when contacted with the substantiallyanhydrous Lewis acids under elevated temperatures form higher boilingcompounds which are readily removed from the alcohol 'by distillation.To'adequately effect a clean up of carbonyl compounds, the substantiallyanhydrous Lewis acid should be employed in an amount from 0.5 to 50grams per liter of alcohol and preferably from 5 to 30 grams per literof alcohol preferably for a period of at least 15 minutes to about 4hours at temperatures from ambient to below the boiling point ofalcohol. Preferred temperatures are 60 to 80 F. These conditions willvary depending on the amount of carbonyl present in the alcohol.

While the anhydrous Lewis acid treatment of the contaminated alcoholdoes not necessarily affect the color of the alcohol per se, the colorof the final ester product, e.g., dialkyl phthalate, is considerablyimproved over that prepared with a non-treated alcohol reactant havingthe same initial quality. Since the treating agent is acidic and isitself a contaminant, it is preferably neutralized and washed from thealcohol with aqueous caustic and water in a conventional manner. Theproduct is then fractionated to obtain an alcohol of extremely highpurity and one having little or no tendency to form color bodies uponesterification.

To demonstrate the effectiveness of the present treatment, reference maynow be had to the following examples (1-3) which compare the presentanhydrous Lewis acid treatment with that of no treatment and plain heatsoaking for both C and C alcohols.

Example 1 A C oxo alcohol containing carbonyl contaminants was dividedinto 3 samples. The first sample was simply distilled in accordance withconventional practice. The second sample was heated for 4 hours at 300F. and distilled under the identical conditions as sample 1 The thirdsample was treated with 20 grams of anhydrous BP per liter atroom'temperature and heated for 4 hours at 300 F. and distilled. Thealcohols were esterified with phthalic anhydride under standardconditions, i.e. 258- 320 F. and with 4 grams/liter of sulfuric acidcatalyst.

I Sample Treatment Ester Color 06 0x0 Alcohol. None (distll1ed) 0. DoHeated, Distilled 0. 26 BFS, Heated, Dist 0. 22

The ester color refers to color readings on a Bausch and Lombcolorimeter scale at 447 mm. light wave against distilled water as astandard. For-an approximate idea of the colors involved, 0.75 is anester which is dark brown in color, 0.26 has a distinct pale yellowcolor, whereas 0.18 is water white to the naked eye.

Example 2 Sample Treatment Ester Color Ow Oxo Alcohol None (distilled)0. 67 Do Heated, Distilled 0.30

Do A1013 Heated, Distilled 0. 22

Example 3 A crude C oxo alcohol obtained by oxonating C olefin was firststabilized by removing light ends containing hydrocarbons, e.g.,olefinic and paraffinic. This alcohol was then separated into twosamples. Sample 1 was heated at 300 F. for 4 hours and distilled; sample2 was treated with 20 grams of anhydrous AlCl per liter 'at roomtemperature, and distilled with the following results:

Sample Treatment Ester Color C Alcohol Heated and Distilled 0. 234 DoA101; Treated, Distilled. 0.190

It is evident from the above three examples that heating coupled withdistillation produced an alcohol of somewhat better quality than thestarting product. However, the final ester colors obtained without theanhydrous Lewis acid treatment, i.e., 0.26, 0.30 and 0.234, are all wellabove specification in that they are distinctly yellow to the eye. Thealcohol treated with anhydrous BF and A101 produced ester colors of 0.22and 0.190 which approach waterwhiteness although these alcohols stillhave some detectable color. In the above examples, extremely pooralcohols were employed to test the efiectiveness of the anhydrous Lewisacid treatment.

To demonstrate the effect of anhydrous Lewis acid treatment on thecarbonyl contaminants of the alcohol and especially correlated to estercolor, reference may be had to Table I which shows treatment of a decylalcohol prior to final fractionation but subsequent to the 1 Precisionlimits on the above tests are 10.02 for carbonyl and $0.20 for estercolor.

It is to be understood that the anhydrous Lewis acid 2 treatment may beapplied to either the finished alcohol product as it comes from thefinal fractionator in the conventional oxo plants or, as will bediscussed in more detail subsequently, it may be applied to the alcoholstream prior to the final fractionator and subsequent to a stabilizerfrom which hydrocarbon and other light ends are removed. In general, thestabilizer feed comes directly from the hydrogenation unit.

To illustrate with more clarity, a complete process for thedecontamination or upgrading of oxo alcohols, reference is now had tothe drawing which sets forth a simplified schematic flow plan of onespecific process which incorporates the acidic treat of the presentinvention. In the drawing, line 1 represents the alcohol feed from thehydrogenation unit of the x0 plant. This stream contains crude 0x0alcohol contaminated with substantial amounts of hydrocarbon, aldehydesand high boiling polymers. The stabilizer 2 rejects hydrocarbon andother light boiling compounds via line 3 and produces relatively pureoxo alcohol via line 4. The alcohol in line 4, however, contains notonly the monomer alcohol product, i.e., C alcohol from C olefin, butalso contains high molecular weight dimer and trimer product sometimesreferred to as oxo bottoms. The bottom stream from the stabilizer passesinto a treating vessel which may be equipped with a stirrer or othersolid liquid contacting means wherein anhydrous AlCl is admixed with thealcohol at a preferred temperature of 60 to 80 F. for a period of /2 to3 hours and at a rate of 5 to 30 grams per liter. The treated alcohol ispassed via line 6 into a wash tower 7 which may comprise several unitsto permit a series of aqueous caustic and water washes to therebyinactivate and remove A1Cl3 or other Lewis acids present. The washedproduct is passed via line 8 into drying column 9 which may be of anytype desired. An economical and simple technique is to have staged phaseseparation with stripp'ng equipment to remove residual water overheadvia line 10. The aqueous water wash layer is removed via line 11 andsubstantially anhydrous alcohol is passed via line 12 into finaliractionator 13. It is desirable and sometimes necessary to removesolids, e.g., alumina, etc., prior to fractionation. This may be done byany conventional filtration procedure. The fractionating column whichmay comprise from to 50 plates separates the heavy product bottoms vialine 14 and the purified decontaminated alcohol via line 15.Temperatures for the fractionator and stabilizer have not been givensince they will obviously vary depending on the particular alcoholemployed. With C oxo alcohol the overhead fraction may bo1l between420-460 F. and the bottoms 460+ and C alcohols these ranges will becorrespondingly lower. It is preferred to carry out this treatment atnear room temperatures, e.g. 6080 F. in order to restrict the action ofthe agent to the aldehydic components.

The above process provides a novel approach to problems relating toalcohol quality and purity especially with regard to the use of thesealcohols as intermediates in the production of plasticizer esters. Thetreating agents are in general very inexpensive and may be incorporatedin existing commercial plants without substantial equip ment cost. Theproduct obtained via this process is not only decontaminated of colorforming bodies but has the added advantage of containing no extraneousadditives such as the various chemical reducing agents.

What is claimed is:

1. A process for purifying C to C alcohols selected from the groupconsisting of 0x0 alcohols and alcohols prepared by the oxidation andsubsequent hydrolysis of aluminum alkyls and containing between about0.01 and about 1.0 wt. percent of carbonyl compound impurities inmixture therewith which consists essentially of contacting said alcoholswith from 0.5 to 50 grams per liter of a substantially anhydrousmaterial selected from the group consisting of aluminum chloride, borontrifluoride and zinc chloride at temperatures from about roomtemperature to below the boiling point of the alcohol for a sufiicienttime to convert said carbonyl compounds to higher boiling compounds,neutralizing the treated alcohol with caustic, washing the neutralizedmixture with water and then distilling the treated mixture to recoverthe purified alcohols overhead substantially free of carbonyl compounds.

2. A process as in claim 1 wherein said material is anhydrous aluminumchloride.

3. A process as in claim 1 wherein said material is anhydrous borontrifluoride.

4. A process as in claim 1 wherein said material is anhydrous zincchloride.

5. In a process for producing substantially pure 0x0 alcohols of fromsix to sixteen carbon atoms per molecule wherein crude oxo alcoholscontaining about 0.01 to about 1.0 wt. percent of carbonyl compoundimpurities are fractionated in a first fractionation zone to removeunreacred hydrocarbons and other light products from said oxo alcoholsand wherein said once fractionated alcohols are subsequentlyfractionated in a second fractionation zone to recover a desired alcoholstream, the improvement which consists essentially of treating the oncefractionated alcohol stream with from 5 to 30 grams per liter of asubstantially anhydrous material selected from the group consisting ofaluminum chloride, boron trifiuoride and zinc chloride at temperaturesfrom room temperature to below the boiling pointof said alcohol for fromabout 15 minutes to about 4 hours to convert said carbonyl compounds tohigher boiling compounds, neutralizing the treated alcohol with causticand washing the neutralized mixture with water and then subjecting theneutralized, washed treated alcohol to said second distillation torecover purified C to C alcohols overhead substantially free of carbonylcompounds.

6. A process as in claim 5 wherein said material is anhydrous aluminumchloride.

7. A process as in claim 5 wherein anhydrous boron tn'fluoride.

8. A process as in claim anhydrous zinc chloride.

said material is 5 wherein said material is References Cited UNITEDSTATES PATENTS 3,007,973 11/1961 Weiseman 260-638 3,232,848 2/1966Johnson 260-643 LEON ZITVER, Primary Examiner. J. E. EVANS, AssistantExaminer.

1. A PROCESS FOR PURIFYING C6 TO C16 ALCOHOLS SELECTED FROM THE GROUPCONSISTING OF OXO ALCOHOLS AND ALCOHOLS PREPARED BY THE OXIDATION ANDSUBSEQUENT HYDROLYSIS OF ALUMINUM ALKLYS AND CONTAINING BETWEEN ABOUT0.01 AND ABOUT 1.0 WT. PERCENT OF CARBONYL COMPOUND IMPURITIES INMIXTURE THEREWITH WHICH CONSISTS ESSENTIALLY OF CONTACTING SAID ALCOHOLSWITH FROM 0.5 TO 50 GRAMS PER LITER OF A SUBSTANTIALLY ANHYDROUSMATERIAL SELECTED FROM THE GROUP CONSISTING OF ALUMINUM CHLORIDE, BORONTRIFLUORIDE AND ZINC CHLORIDE AT TEMPERATURES FROM ABOUT ROOMTEMPERATURE TO BELOW THE BOILING POINT OF THE ALCOHOL FOR A SUFFICIENTTIME TO CONVERT SAID CARBONYL COMPOUNDS TO HIGHER BOILING COMPOUNDS,NEUTRALIZING THE TREATED ALCOHOL WITH CAUSTIC, WASHING THE NEUTRALIZEDMIXTURE WITH WATER AND THEN DISTILLING THE TREATED MIXTURE TO RECOVERTHE PURIFIED ALCOHOLS OVERHEAD SUBSTANTIALLY FREE OF CARBONYL COMPOUNDS.